Snow or No....Still A Close Call

Advisories and warnings are out for parts of the Delaware Valley with the upcoming winter spring weather event that's going to move through the region over the next 30 hours.   Winter weather advisories are out for Bucks, the Lehigh Valley, and Berks for tonight and tomorrow morning.   Winter Storm Warnings are out for the Poconos through Thursday morning.   No advisories are out for Philadelphia or South Jersey.

The event that's poised to hit is about 10 hours away, likely to move in after 3 AM tonight.     This event will start as a mixed bag for chunks of the region --particularly around Philadelphia and the northern burbs, with mostly snow farther north.

Computer guidance still holds to the three camps that we outlined in prior posts -- with the NAM the coldest of the guidance and the GFS the warmest.    There is some certainty in the models showing a mixed bag at the front end...that should move in on Wednesday morning, with a sleet/snow/rain mix in the city and suburbs, snow/sleet mix in the northern parts of Bucks/Montgomery County, and snow farther north.   The main brunt of Wednesday morning's precipitation will reside to the north of the city initially but with more precipitation slugging in from the west we'll see everyone get precipitated on throughout the course of the midday and afternoon hours.

This looks to be an elevation dependent event as well -- meaning the higher up you are the better your odds for snow.   This could be a situation where some of the higher hills in Bucks and Montgomery County get an inch or so while lower elevations get rain during the morning round of the storm.   The heavier the precipitation is on the front end of the storm tomorrow the better the odds for some snow, especially north, as colder air aloft gets pulled down through the atmosphere.  

We should see a transition to rain from south to north -- with solely rain falling for a time in the Lehigh Valley and perhaps the southern parts of the Poconos.   This transition time could occur when precipitation may be lighter in intensity during the later afternoon hours -- could be drizzly in some spots as well.  The question then turns to Wednesday night, with the NAM (above) being the exception to the computer guidance consensus in showing a heavy swath of precipitation moving through that could lead to a transition of rain to snow even down into Philadelphia.  Again, the NAM is an exception...with the GFS and Euro not showing this heavy swath of precipitation at all.

Precipitation totals should average out to no more than an inch in many locations -- the highest will be north of the city where it could be more snow than not -- with a half to three-quarters common across the immediate city and suburbs, less than that south.

Regarding snowfall, our projected totals are elevation dependent but we think the best chances for heaviest snows are over the higher elevations of the Poconos.  I can see 3-6" of snow across there and Northeastern Pennsylvania.  Across the Lehigh Valley, 1-3" looks like a reasonable bet.  An inch is possible across the upper parts of Bucks and Montgomery Counties, perhaps even into Chester County's higher elevations.     Snow/sleet mix can't be ruled out into Philadelphia at the start of the event...and if the NAM is correct, it may end as that as well.

We'll provide another update on the storm tomorrow morning.